Transmission of Human Immunodeficiency Virus (HIV) occurs primarily via the mucosal routes, emphasizing HIV-1 vaccines must need to engender mucosal immune responses. However, mucosal immunization has been limited by the ability to deliver intact vaccine antigens across the mucosal barrier for induction of effective mucosal immunity. The long-term goal of this proposal is to determine whether the IgG transcellular pathway represents a novel delivery path for a subunit vaccine against infections of HIV and AIDS-related opportunistic pathogens. The goal of the project derives from the recent proof of concept that the neonatal Fc receptor (FcRn) mediates the bi-directional transport of IgG across polarized epithelial cells. FcRn was initially considered to transport maternal IgG to a fetus through the placenta or to newborns via the intestine. However, FcRn is expressed in a variety of tissues and cells in adult humans and animals; IgG is a predominant isotype of immunoglobulins in the lower respiratory and genital tract. Based on these evidences, we will test the hypothesis that using IgG transport pathway, FcRn can deliver HIV-1 antigen fused to an IgG-Fc across the mucosal barrier to the underlying mucosa-associated lymphoid tissue. The consequences of such transport could induce local immunity able to neutralize the virus at their port of entry and systemic immunity able to prevent systemic spread of the infection. HIV envelope glycoprotein gp120 will be used to probe immune responses to such immunization and to define protective immune responses. The specific aim of this proposal is to determine the ability of FcRn to deliver gp120-Fc antigen across the genital or the respiratory mucosal barrier to engender protective immunity against mucosallv-inoculated virus challenge. Data generated herein will provide valuable information not only for design of a HIV vaccine, but also for general vaccine strategy targeting AIDS-associated opportunistic pathogens or other pathogens, such as cytomegalovirus, herpes simplex virus, mycobacterium, chlamydia, influenza, etc., that infect at or invade across mucosal surfaces. [unreadable] [unreadable] [unreadable]